The invention relates generally to railway car truck friction damping arrangements, and more particularly to a railway car truck friction shoe.
The present invention is directed to a friction wedge or shoe for a railroad car truck and in particular to a friction shoe including a body having a sloped face and a vertical face. The friction shoe dissipates energy throughout the range of suspension travel and friction shoe and bolster velocities moving vertically along the side frame column wear plate.
Railroad car trucks of a design known as a three piece railway car truck include a pair of spaced apart side frames and a bolster that extends transversely between the side frames. The bolster is resiliently supported at each end on a respective side frame by a plurality of suspension springs. Wedge shaped friction shoes are used in such railroad car trucks to dampen movement of the bolster with respect to the side frame of the railroad car truck. Friction shoes are usually generally triangular wedge shaped such that two laterally spaced sloped faces are each in contact with laterally spaced sloped faces of the bolster. The friction shoe is also comprised of a vertical face that is in contact with a corresponding wear plate mounted on a vertical face of a side frame column. Accordingly, the friction shoe acts as a motion damping wedge between the bolster and the wear plate on a vertical column of the side frame.
The friction shoe also is comprised of a bottom section that joins the vertical face and the two laterally sloped faces.
The wear plate on the vertical column of the side frame is usually comprised of steel. The friction shoe is typically wedged into engagement between the sloped faces of the bolster and the vertical column of the side frame by a pair of concentrically arranged suspension springs. The bottom section of the friction shoe includes a protrusion which serves to constrain and locate the suspension springs. Resistance to sliding movement of the friction shoe with respect to the side frame, which in turn provides dampening of vertical bolster movement, is provided by the frictional forces generated between the friction shoe vertical face and a wear plate on the side frame vertical column.
It is an object of the present invention to provide an improved railway car truck friction shoe that allows the use of an additional concentrically nested spring to increase the damping frictional force on the vertical movement of the bolster for better control with greater energy dissipation. The bottom section includes a spring lug in the form of a hollow protrusion extending from the bottom section. This spring lug not only constrains and locates an outer and middle pair of suspension springs, but also the bottom surface of the lug is flat and smooth and is designed to engage a third concentrically arranged inner suspension spring. Additionally, the spring lug is hollow and as a result facilitates manufacturing of the friction shoe as the central hole helps locate the sand core that forms the hollow interior of the friction shoe. Further, the bottom center of the spring lug is open which allows water or other debris to pass through the friction shoe instead of collecting inside it.